Exploiting Radio Frequency







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Radio frequency is the transmission medium over which 802.11 rides. If the medium is hacked, whatever it carries is disrupted, much like how torpedoing an ocean liner would probably kill many people onboard. So, if 802.11 is a train, then radio frequency (RF) is the rail tracks on which the train rides. RF is electromagnetic radiation that is either induced or radiated when an electrical current passes through an antenna, which is a device designed to emit or receive electromagnetic waves. All the higher-level protocols such as 802.11 (WiFi), 802.15 (Bluetooth), and 802.16 (WiMax) are embedded in the electromagnetic energy pulses that emanate from antennae. Thus, understanding the characteristics of RF is essential to understanding how hackers can conduct RF-based exploits.

RF exists as a waveform signal with frequency and amplitude and is subject to noise and other forms of signal loss (attenuation). In practical terms, this is evident when a WNIC simply moves out of range of the AP it was previously associated with. The AP's electromagnetic energy emitted from its antenna that reaches the WNIC's antenna has been degraded to the point where it becomes unrecognizable to the WNIC that is trying to decode the received signal. Thus, the operating system of the laptop housing the WNIC reports "no signal" because the embedded higher-layer protocol information is no longer recognizable to the signal processing algorithm on the WNIC. To understand why an RF signal degrades and what causes degradation, let's look at some of the terms just mentioned in a little bit more detail.

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